The use of mobile pressure vessels to transport dry granular bulk cement are routinely used in the treating of oil and gas production wells. Typically, prior art vessels have a toriconical, or funnel, shaped bottom portion, a vertical cylindrical side wall, and a torispherical, or dome shaped, top portion. The vessels are typically mounted in tandem on a truck bed or on a tractor trailer, whereupon the vessels can be transported to and/or stored at the site of an oil or gas well. The vessels are designed to allow cement to be loaded into the vessel via a re-closable hatch located on the domed top portion of the vessel prior to being transported to the well site and/or while the vessels are located at the well site. Some prior art vessels are additionally designed to allow for the pneumatic conveyance of the cement into the vessel. Cement is conveyed out of the vessel via an external air supply and aerators and plumbing located within and about the vessels. After being conveyed out of the vessel, the cement is routinely piped into a separator, which serves to reduce and/or eliminate cement plug flow and unwanted cement dust. The cement is then ultimately piped to a mixer where cement, water, and perhaps selected additives are mixed together prior to being pumped downhole.
All too often, during, or in preparation of the conveyance of the cement located within vessels at a job-site, it becomes necessary to gain access to the interior of the prior art vessels to dislodge cement that has become lodged within the vessel for one reason or another including the cement adhering, or caking, to itself or to the sidewalls of the vessel. In order to gain access to the interior of the vessel for inspection, to check on the condition of the cement currently therein, or to attempt to dislodge caked cement, an equipment operator may have to scramble onto the top of the vessel to reach through the hatch located thereon. At a minimum this is an inconvenience, and during inclement weather, scrambling on the domed-shaped top of a vessel having ice or rain on the outer surface can pose a hazard to the operator.
Thus, there is a need for a mobile bulk cement pressure vessel in which access can be gained to the interior thereof with a minimum of inconvenience and to minimize any loss of footing to the operator.
Another shortcoming with prior art mobile bulk cement pressure vessels, especially with vessels mounted in a tandem arrangement, that is one vessel mounted longitudinally in front of the other, is that each vessel, or tank, is specifically constructed to be mounted at the forward position or aft position of the truck body, trailer, or other mobile platform. Each vessel also accommodates manifolding, piping, and venting specific to either the forward mounted vessel or the aft mounted vessel. For example, certain piping will be positioned on the forward tank and the rearward tank for removing the bulk material, or cement, from the tanks and introducing it to a separator which is often located aft of the rearward vessel. Economics and physical limitations usually require that the piping be routed by the most direct route, and thus each vessel will have ports and piping designed specifically for that vessel's location. Therefore, in a typical tandem vessel arrangement, there will be a forward vessel, with appropriately located mounting lugs and ports, and a rearward vessel also having appropriately located mounting lugs and ports. Such an arrangement requires the design and fabrication of two differing, location-specific separate vessels, as well as the costs and time required for obtaining pressure vessel code approval and for maintaining and updating revised shop and maintenance drawings for each vessel and respectively specific piping and manifolding.
Furthermore, when a particular vessel, or component, must be replaced, it must be ordered by a specific part number or other means of positive identification. For example, it must be made clear whether a forward positioned vessel or component is needed, or whether a rearward positioned vessel or component is needed, from either the original fabricator or a regional warehouse. This can become quite a chore and inconvenience when a particular vessel or related component is damaged in remote field locations throughout the world as such locations often times have less than ideal communication and transportation links.
Thus, there is a need for bulk material transport and storage units that may readily be used in a tandem arrangement in either a forward position or a rearward position to reduce the necessity of designing and fabricating two different vessels to meet applicable pressure vessel codes, as well as maintaining and warehousing bulk material vessels and related components specifically designed and constructed for particular locations on a truck body, trailer, or other mobile platform.